Things You'll Need
Pentas, or the Egyptian star flower, grow as a perennial in subtropical areas or regions that don't experience frost. In climates with four seasons, pentas are treated as an annual. The plants reach their full height of 4 feet in perennial zones, growing as a small shrub at maturity. Annual-grown pentas remain smaller, typically reaching no more than 1 to 2 feet tall. Whether you grow the plants as annuals or perennials, they all feature star-shaped blooms and deep green foliage that adds color to the garden all summer long.
Grow pentas in a well-drained bed with rich soil. The plants flower best in beds that receive six or more hours of sunlight per day, but they can tolerate partial shade if necessary.
Water the pentas plants once a week with a deep watering that moistens the top 6 inches of soil. The plants don't require watering if there is at least 1 inch of rainfall in the preceding week.
Feed the plants every four weeks in the summer with a soluble fertilizer formulated for flowering garden plants. Apply the fertilizer at the rate recommended for your flower bed size. Regular fertilization encourages lush foliage and optimum flowering.
Spread a 4- to 6-inch layer of mulch over the plants in fall after they die back naturally to overwinter them in U.S. Department of Agriculture plant hardiness zone 8, or other locations that only receive light winter frost. Cover the crown of the plant to protect the pentas' roots from cold weather. Pentas don't require mulching in tropical areas where they remain evergreen, or in freezing areas where they die back completely.
Remove the mulch in spring after frost danger is past. Cut back the old dead stems and foliage to a 6-inch height. The plants produce new stems and foliage from the base, regrowing and flowering again in summer.
Pentas are typically planted from nursery bedding plants, as they don't start readily from seed.
When planting new pentas beds, space standard varieties 18 to 24 inches apart and dwarf varieties 10 to 14 inches apart.